178 THE STRUCTURE OF EVOLUTIONARY THEORY
and truly a discredit to the memory of a man and his much more comprehensive
system. In any case, the changes wrought by new habits during an organism's
lifetime can be passed directly to offspring in the form of altered heredity. Soft
inheritance may have been the standard belief of the time, but Lamarck certainly
recognized its crucial and particular role in his system. He wrote with his
characteristic lack of doubt (1815, in Burkhardt, 1984, p. xxix): "The law of nature
by which new individuals receive all that has been acquired in organization during
the lifetime of their parents is so true, so striking, so much attested by the facts,
that there is no observer who has been unable to convince himself of its reality."
Lamarck abstracts his idea of inheritance as two principles, usually printed in
italics in his texts to emphasize their importance, and known ever since as:
- use and disuse
- the inheritance of acquired characters (1809, volume 1, p. 113)
Even if this theory of inheritance ranked as folk wisdom of the day,
Lamarck's revolutionary statement, one of the great transforming insights in the
history of human thought, resides in the preceding principle that translates this
mode of inheritance into a theory of evolution—the triggering of change in form
by prior alterations in behavior. Lamarck clearly recognized the central role of this
claim, for he always cited this counterintuitive sequence of causality—from altered
environments to changed habits to modified form—as the linchpin of his entire
system. In the Philosophie zoologique, he quotes his own earlier statement from
the Recherches of 1802: "It is not the organs, that is to say, the nature and shape of
the parts of an animal's body, that have given rise to its special habits and faculties;
but it is, on the contrary, its habits, mode of life and environment that have in
course of time controlled the shape of its body, the number and state of its organs
and, lastly, the faculties which it possesses" (1809, p. 114). Lamarck then makes
his threefold causal chain—environment to habits to form—even more explicit
(1809, p. 126): "This is a fact that can never be disputed; since nature shows us in
innumerable other instances the power of environment over habit and that of habit
over the shape, arrangement and proportions of the parts of animals."
Causality might run from altered environment to changed organism, but
Lamarck insisted that he did not view organisms as passive writing slates, ripe for
inscription by the modifying hand of environment. Environmental change
translates to adaptation of form only through the intermediary of organic action
expressed, in higher creatures at least, as altered habits: "Whatever the
environment may do, it does not work any direct modification whatever in the
shape and organization of animals. But great alterations in the environment of
animals lead to great alterations in their needs, and these alterations in their needs
necessarily lead to others in their activities. Now if the new needs become
permanent, the animals then adopt new habits which last as long as the needs that
evoked them" (1809, p. 107).
These statements about the responses of animals to "felt needs" (Lamarck